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KOMUNIKASI DATA

PENGANTAR TEKNOLOGI INFORMASI

Telecommunications Systems

Data Communication : High speed data exchange between computers and/or other electronic devices via cable or wireless.(BussinesDictionary.com)

Telecommunications can be defined as communication of data and information by electronic means such as telephone, radio, television, and computer, usually over some distance

Computer communications : a process in which one computer transfers data, information and instructions to another computer

Telecommunications system is a collection of compatible hardware and software arranged to communicate data, information and instructions from one location to another

Telecommunications systems can transmit text, graphic images, voice, and video information through communications channel

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Contoh sistem telekomunikasi

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Telecommunications Systems(cont.)

Model telekomunikasi

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A sending device that initiates an instruction to transmit data, information, or instructions. It can be a computer system, a terminal, a cellular telephone, a WebTV, a GPS receiver, an Internet-enabled PDA, or another device that originates the message.

A communications device that connects the communications channel to a sending device.

A communications channel or transmission media on which the data, instructions, or information travel.

A communications device that connects the communications channel to a receiving device.

A receiving device that accepts the transmission of data, information, or instructions.

A communications software that controls and manages the activities and functions of the communications network.

The telecommunications model consists of the following:

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Telecommunications System Components

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Devices that handle the movement of data in a computer network include:

modem

Router

Hub

Network interface cards

Multiplexer

Front-end processor

Host computer

MODEM (Modulation/Demodulation)

Connects a communications channel to a sending or receiving device

Computers process data as digital signals.

Data, instructions, and information travel along a communication channel in either analog or digital form

Modem converts analog to digital signals and digital to analog signals

Converting signal from digital to analog is called modulation

converting signal from analog to digital is called demodulation

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Telecommunications System Components(cont.)

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es 1. Dial-up modem

• usually is in the form of an adapter card that you insert in an expansion slot on a computer's motherboard

• One end of a standard telephone cord attaches to a port on the modem card and the other end plugs into a telephone outlet

2. Cable modem • a digital modem that sends and

receives digital data over the cable television (CATV) network

• A cable modem usually is an external device, in which one end of a cable connects to a CATV wall outlet and the other end plugs in a port in the system unit


3. wireless modem

• allows access to the Internet wirelessly from a notebook computer, a PDA, a smart phone, or other mobile device

• Wireless modems, which have an external or built-in antenna, typically use the same waves used by cellular telephones


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DEVICES CONNECTING NETWORKS

Network bridging provides an easy way to connect 2 or more network to become a single big network without using router in order to share file, printer or Internet connection.

Please note that all computers in different network that needs to be bridged must sit in same logical IP network.

1. bridge


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2. gateway a communications processor that

connects networks that use different protocols by providing the translation from one set of protocols to another

3. router

an intelligent bridge for large networks

connect multiple networks and routs communications traffic to the appropriate network using the fastest available path

many routers are protected by a built-in firewall


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4. front-end processor

a small computer dedicated to communications management and is attached to the main, or host, computer in a large computer system

The front-end processor is largely responsible for collecting and processing input and output to and from terminals and grouping characters into complete messages for submission to the CPU of the host computer

5. network card/network interface card (NIC)

is an adapter card, that enables the computer or device that does not have built-in networking capability to access a network


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6. repeater

a device that accepts a signal from a transmission medium, amplifies it, and retransmits it over the medium

As a signal travels over a long distance, the signal undergoes a reduction in strength, an occurrence called attenuation

7. hub or switch

a device that provides a central point for cables in a network

receives data from many directions and then forwards it to one or more destinations


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Communications Channels communications path between

two devices. composed of one or more

transmission media The amount of signals that can

travel over a communications channel sometimes is called the Bandwidth

Baseband transmission media can transmit only one signal at a time

broadband media can transmit multiple signals simultaneously


Transmission media are one of two types: physical or wireless

Physical transmission media use wire, cable, and other tangible materials to send communications signal

Wireless transmission media send communications signals through the air or space using radio, microwave, and infrared signals

Physical transmission media used in communications include twisted-pair cable, coaxial cable, and fiber-optic cable

These cables typically are used within building or underground between buildings


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1. twisted-pair wire cable consists of one or more twisted-pair wires bundled together The wires are twisted together to reduce noise, which is an electrical

disturbance that can degrade communications shielded twisted-pair (STP) cable, has a metal wrapper around each

twisted-pair wire, which further reduces noise Cables that do not have this shielding are called unshielded twisted-

pair (UTP)

Physical Transmission Media


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2. coaxial cable consists of a single copper wire

surrounded by at least three layers:

• an insulating material,

• a woven or braided metal, and

• a plastic outer coating

3. fiber-optic cable

consists of dozens or hundreds of thin strands of glass or plastic that use light to transmit signals

Each strand, called an optical fiber advantage include (1) capability of carrying

significantly more signals; (2) faster data transmission; (3) less susceptible to noise from other devices; (4) better security for signals during transmission; and (5) smaller size


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The speeds of various physical communications media when they are used in LANs


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Wireless Transmission Media

Wireless transmission media used in communications include broadcast radio, cellular radio, microwaves, communications satellites, and infrared

1. Broadcast radio

a wireless transmission medium that distributes radio signals through the air over long distances

Bluetooth, Wi-Fi, UWB, and WiMAX communications technologies use broadcast radio signals


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2. Celular radio

a form of broadcast radio that is used widely for mobile communications, specifically wireless modems and cell phones

Several categories of cellular transmissions exist, defining the development of cellular networks:

• 1G (first generation) transmitted analog data

• 2G (second generation) transmit digital data at speeds from 9.6 kbps to 19.2 kbps

• 3G (third generation) transmit digital data at speeds from 114 kbps to 2.4 Mbps

• 4G (fourth generation) transmit digital data at speeds up to 15 Mbps

3G technology allows users quickly to display multimedia and graphics, browse the Web, watch television or a video, have a video conference, and transfer data on a cellular device


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3. microwafe

high-frequency radio waves that are sent through the atmosphere and space

Microwaves provide a high-speed signal transmission, and can transmit data at rates up to 4,500 times faster than a dial-up modem

Microwaves are limited to line-of-sight transmission, which means that microwaves must be transmitted in a straight line with no obstructions between microwave antennas

To avoid possible obstructions, such as buildings or mountains, microwave stations often sit on the tops of buildings, towers, or mountains

Microwave signals can carry thousands of channels at the same time.


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4. communications satellite

basically a microwave station placed in outer space

The satellite receives the signal from the earth, amplifies the relatively weak signal, and then rebroadcasts it at a different frequency to any number of earth-based stations

Transmission from an earth-based station to a satellite is an uplink

Transmission from a satellite to an earth-based station is a downlink

The advantage of satellite communications is the ability to receive and broadcast over larger geographic regions


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5. infrared

a wireless transmission media that sends signals using infrared light waves

Infrared transmission requires a line-of-sight transmission and short distances -- under a few hundred yards

Infrared transmission can be used to connect various devices and computers.

For example, infrared transmission has been used to allow handheld computers to transmit data and information to larger computers within the same room

This means of transmission can be used to establish a wireless network with the advantage that devices can be moved, removed, and installed without expensive wiring and network connections


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Communications software

consists of programs that help users establish a connection to another computer or network; manage the transmission of data, instructions, and information; provide an interface for users to communicate with one another

A set of rules and procedures governing transmission between components in a network is called a protocol

The principal functions of protocol in a network include: identifying each device in the communication path securing the attention of the other device verifying correct receipt of the transmitted message determining that a message requires retransmission if it is

incomplete or has errors performing recovery when errors occur


Ethernet

a network standard that specifies no central computer or device on the network (nodes) should control when data can be transmitted

each node attempts to transmit data when it determines the network is available to receive communications

If two computers on an Ethernet network attempt to send data at the same time, a collision will occur, and the computers must attempt to send their messages again

Ethernet is the popular communications protocol often used with local area networks (LAN) because it is relatively inexpensive and easy to install and maintain

A more recent Ethernet standard, called Fast Ethernet , 10-Gigabit Ethernet


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Token Ring

another popular network standard for LANs.

Token ring is based on ring topology (although it can use a star topology)

Some token ring networks connect up to 72 devices

The data transfer rate on a token ring network can range from 4 Mbps to 1 Gbps

Transmission Control Protocol/Internet Protocol (TCP/IP)

a network standard that defines how messages (data) are routed from one end of a network to the other, ensuring the data arrives correctly

TCP/IP has been adopted as a network standard for Internet communications.

TCP provides transport functions, ensuring, among other things, that the amount of data received is the same as the amount transmitted

IP provides the addressing and routing mechanism that acts as postmaster


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TCP/IP’s four-layer reference model:

Application layer serves as the window for users and application processes to access network services

Transport layer handles end-to-end packet transportation

Internet layer formats the data into packets, adds a header containing the packet sequence and the address of the receiving device, and specifies the services required from the network.

Network interface layer places data packets on the network for transmission


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The TCP/IP suite of applications includes five protocols:

Simple Mail Transfer Protocol (SMTP): It is TCP/IP s own �messaging system for e-mail.

File Transfer Protocol (FTP): It allows files containing text, programs, graphics, numerical data, and so on to be downloaded off or uploaded onto a network.

Telnet Protocol: It provides terminal emulation that allows a personal computer or workstation to act as a terminal, or access device, for a server.

Hypertext Transfer Protocol (HTTP): It allows Web browsers and servers to send and receive Web pages.

Simple Network Management Protocol (SNMP): It allows the management of networked nodes to be managed from a single point.


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802.11 (Wi-Fi)

developed by IEEE, is a series of network standards that specifies how two wireless devices communicate over the air with each other

The 802.11 standard often is called the wireless Ethernet standard because it uses techniques similar to the Ethernet standard to specify how physically to configure a wireless network

The term Wi-Fi (wireless fidelity) identifies any network based on the 802.11 series of standards

Windows Vista and Windows Mobile include support for Wi-Fi. Most of today's computers and many personal mobile devices are Wi-Fi enabled.


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Bluetooth

a network standard that defines how two Bluetooth devices use short-range radio waves to transmit data

The data transfers between devices at a rate of up to 3 Mbps To communicate with each other, Bluetooth devices often must be

within about 10 meters but can be extended to 100 meters with additional equipment. Windows Vista has built-in Bluetooth support.

UWB

stands for ultra-wideband, is a network standard that specifies how two UWB devices use short-range radio waves to communicate at high speeds with each other

At distances of 10 meters (about 33 feet), the data transfer rate is 110 Mbps. At closer distances, such as 2 meters (about 6.5 feet), the transfer rate is at least 480 Mbps

Because of its high transfer rates, UWB is best suited for transmission of large files such as video, graphics, and audio.


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IrDA

a standard for transmitting data wirelessly to each other via infrared light waves

he devices transfer data at rates from 115 Kbps to 4 Mbps between their IrDA ports

Infrared requires a line-of-sight transmission, which means that the sending device and the receiving device must be in line with each other so that nothing obstructs the path of the infrared light wave

RFID

a standard that defines how a network uses radio signals to communicate with a tag placed in or attached to an object, an animal, or a person

An active RFID tag contains a battery that runs the chip's circuitry and broadcasts a signal to the RFID reader

A passive RFID tag does not contain a battery , can be small enough to be embedded in skin


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RFID toll collection


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WiMAX (Worldwide Interoperability for Microwave Access)

also known as 802.16, is a newer network standard developed by IEEE that specifies how wireless devices communicate over the air in a wide area

Using the WiMAX standard, computers or devices with the appropriate WiMAX wireless capability communicate via radio waves with other computers or devices via a WiMAX tower.

Fixed wireless WiMAX has data transfer rates up to 40 Mbps, while mobile wireless WiMAX has data transfer rates up to 15 Mbps.

WAP (Wireless Application Protocol )

standard that specifies how some mobile devices can display the content of Internet services such as the Web, e-mail and chat rooms

On WAP-enabled devices, data transfer rates range from 9.6 to 153 Kbps depending on the type of service


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Data Transmission

Signal Type: Analog or Digital

Sig

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Transmission Modes: Asynchronous and Synchronous

Asynchronous transmission transmits one byte at a time over a line at random intervals, each byte framed by controls -- a start bit for marking the beginning of the byte, a stop bit for marking the end of the byte, and a parity bit for error checking. Asynchronous transmission is relatively slow and used for low-speed transmission.

Synchronous transmission transmits groups of bytes simultaneously at regular intervals, with the beginning and ending of a block of bytes determined by the timing circuitry of the sending device and receiving devices. it provides much higher speeds and greater accuracy than asynchronous transmission

Data Transmission(cont.) T

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Transmission Direction

Simplex transmission sends data in one direction only. One example of simplex transmission is television broadcasting.

Half-duplex transmission allows data transmission in either direction, but only one way at a time. Many fax machines, credit card verification systems and automatic teller machines use half-duplex transmission.

Full-duplex transmission, data can flow in both directions at the same time. A regular telephone line, for example, supports full-duplex transmission, allowing both parties to talk at same time.

Multiplex transmission, several different types of signals can be carried at once through the same line.

Data Transmission(cont.) T

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Networks 1.

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A network is a collection of computers and devices connected by telecommunications channels that allows users to facilitate communications, and to share data, information, software, and hardware with other users.

A network topology is a description of the possible physical connections within a network

Network Topologies

In a network topology, a component is called a node, which refers to any device connected to a network, including the server, computers, telephones, and other devices

Three commonly used network topologies are bus, ring, and star.

1. Bus network

consists of a single central cable, to which all the network nodes are attached

The bus is the physical cable that connects the computers and other devices.

when a sending device transmits data, address of the receiving device is included with the transmission so that the data is routed to the appropriate receiving device

only one node can transfer items at one time

If one node in the network fails, none of the other nodes in the network is affected

Networks(cont.) 1.

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2. Ring network

links all nodes together in a circular chain

Data messages travel in only one direction from device to device around the entire ring

The node examines any data that passes by to see if it is the addressee; if not, the data is passed on to the next node in the ring

If a node on a ring network fails, all nodes before the failed node are unaffected, but those after the failed nodes cannot function

Networks(cont.) 1.

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Networks(cont.)

3. Star network

all of the computers and devices (nodes) on the network connect to a central device, thus forming a star

Two types of devices that provide a common central connection point for nodes on the network are a hub and a switch

Star networks are fairly easy to install and maintain

if one node fails, only that node is affected

if the hub computer fails, the entire network fails

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Networks(cont)

LAN, MAN, and WAN

Usually, networks are classified ad a local area network, metropolitan area network, or wide area network

1. local area network (LAN)

a network that connects computers in a limited geographical area, such as a school computer laboratory, department, or closely positioned group of buildings

A local area network can be a ring, bus, or star network.

A wireless LAN (WLAN) is a LAN that uses no physical wires.

Networks(cont.)

2. Metropolitan area network (MAN)

Metropolitan area network (MAN) connects LANs in city or town

it connects local area networks in a metropolitan area

A MAN usually is managed by a consortium of users or by a single network provider who sells the service to the users

3. wide area network (WAN)

a network that covers a large geographical area using a communications channel that usually combines many different types of transmission media

A WAN can be one large network or can consist of two or more LANs connected together

The Internet is the world's largest WAN

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Networks(cont.)

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Networks(cont.)

The design of computers, devices, and media in a network, sometimes called the network architecture

Network Architectures

1. client/server network a network in which one or more computers

are designated as a server(s) and other computers on the network, called clients, can request services from the server, such as providing database access or queuing print jobs

A server, also called host computer, controls access to the hardware and software on the network and provides a centralized storage area for programs, data, and information

The other computers (clients) on the network rely on the servers for these resources, such as files, devices, processing power, and storage

Networks(cont.)

2. peer-to-peer network

a simple, inexpensive network

All computers in a peer-to-peer network have equal status; no one computer is in control

Each computer, called a peer, in the network can share the hardware, data, or programs located on any other computer in the network

Each computer stores files on its own storage devices

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